The term “fluidically” is in particular understood to mean hydraulically or pneumatically. The term “fluid” is accordingly understood to in particular refer to a hydraulic fluid or to compressed air.
Such a disk brake system is referred to as “fail safe” because, in the worst case, what is expected in the event of a defect is a decline in the fluid pressure applied to the brake cylinders. This leads to brake activation and thus prevents an uncontrolled state of movement. This is described, for example, in DE 10 2007 041 411 B3, DE 10 2006 003 832 A1, DE 36 04 451 A1 and DE 32 04 695 A1.
A lifting device having such a disk brake system is described, for example, in WO 03/072904 A1. This lifting device serves to increase and decrease a load, in particular with drilling equipment or a pipe plugging closing device, for example, from a floating platform on the bottom of the ocean or in or on a borehole. It has a rotatably mounted winding drum which is attached to a flexible traction device, which is usually made of a steel cable that can be wound and unwound by a rotational drive of the winding drum. The winding drum is connected to a brake disk of the disk brake system. The rotational speed of the winding drum can be decreased or even completely blocked during the unwinding operation with the help of the brake cylinder pairs that are provided with a plurality of brake calipers.
To be able to influence the braking force, the pressure applied to each brake cylinder must be adjusted in the same way, to which end, in the simplest case, the first and second fluid connections of all brake cylinders must merely be connected in parallel with the same fluid pressure source.
Safety regulations require, however, that, for testing purposes, the brake cylinder pairs must be activatable or deactivatable either individually or jointly in various combinations. To do so with known disk brake system, the first fluid connections of the two brake cylinders of a brake cylinder pair must be connected to a first pressure line, while the two second fluid connections must be connected to a second pressure line. Each pressure line comprises a separate 2/2-way valve which can be operated electromagnetically against a spring force. The 2/2-way valve is designed so that it is also currentless in the forward-voltage position under the influence of the spring force.
One disadvantage with such a disk brake system is the installation cost associated with the individual 2/2-way valves. Operational reliability is also negatively influenced by any leakage which may occur in the fluid lines between the 2/2-way valves and the brake cylinders.